脉冲火焰光度检测器分析水中有机磷农药

Analysis of Trace Organophosphorous Pesticide in Water Using Pulsed Flame Photometric Detector

介绍一种新的有机磷农药GC分析检测器PFPD,考查了积分时间、柱流速、进样溶剂对GC/PFPD测定的影响。结果表明,在注入量0.04～2000ng范围内,注入量与GC响应间呈良好的线性关系,最低检出量为甲基对硫磷和对硫磷0.01ng,乐果和敌敌畏0.02ng。GC/PFPD结合固相萃取技术可满足环境水样中微量有机磷农药残留的分析要求。

Organophosphorous pesticides (OPs), one kind of the effective and broad-spectrum insecticides, are presently widely used in agriculture and storage, which cause the pollution of surface water and groundwater. Because pesticides are usually at very low levels and the samples are often complex, it is difficult to detect and quantitate them using common detectors. The detectors most commonly used for the analysis of the OPs are the NPD, FPD and MS. All of these detectors have limitations in the analysis of the complex matrixes often encountered in pesticides analysis. The low concentrations of OPs usually found in water make necessary the use of very sensitive and selective techniques for trace analysis. Pulsed flame photometric detector (PFPD), a new kind of detector used in GC analysis of OPs, was introduced in this paper. It uses a flame that is repetitively ignited and extinguished instead of a continuously burning flame. The use of pulsed flame instead of a continuous flame adds the time dimension to flame photometric analysis as well as wavelength selectivity. Compared to a standard flame photometric detector (FPD), quenching is reduced in PFPD. Such factors as integrating time range, column flow rate and solvents were examined. Among these factors, solvent is most important. Multiple peaks occur for dichlorvos and dimethoate when methanol is used as solvent. Dichloromethane as solvent increases thePFPD noise and decreases the sensitivity and detection limit. Acetone, hexane and ethyl acetate can be used as injection solvents. Response versus the amount of pesticide injected ranging from 0.04～2 ng showed a good linearity. The detection limits were 0.01ng for parathion and parathion-ethyl, 0.02 ng for dichlorvos and dimethoate. Prior to GC analysis of water samples of low OPs concentration, we use solid-phase extraction with activated carbon fiber (ACF) as adsorbent to enrich target compounds. For 1 liter of water sample spiked with OPs (concentration 0.1μg·L-1), 0.2 g of ACF and 8 mL dichloromethane (eluent) are needed. The eluent was evaporated on a nitrogen stream at 35 ℃to 1ml and replaced by 1mL ethyl acetate. 1 μL of aliquots were chromatographed on GC/PFPD. Extraction recovery rates ranges from 80%to 118%. The method developed can meet the need of analysis of trace OPs in water sample.